40 min is tight but doable.

But the funny thing to me is as much as people here complain about tight connections being offered, and I get it, I don't like less than an hour...I had at least a dozen people ask me over the years if I could break married segments to book them below MCT connections. So those tight connections exist because there are plenty of people who want the tightest connection possible and will happily save 30-90 min per connection for the couple of times they'll enevitably misconnect.

So it's not that DL hates you and wants you to miss your flight. It's just responding to a certain segment of customer demand.

That said I still wouldn't book under an hour